Circuit breakers are important components of many electronic systems, such as power supplies. Circuit breakers commonly comprise a movable electrical contact and a stationary contact. The movable electrical contact is typically coupled to an electromagnetic device that opens the breaker contacts when an over-current condition is detected. During normal circuit operation an actuator mechanism couples the stationary and movable breaker contacts so that the circuit breaker is in a conducting, or on-state. However, when an over-current condition is detected, the circuit breaker trips and the actuator mechanism separates the breaker contacts so that the circuit breaker enters a non-conducting, or off-state.
FIG. 1 is a perspective view of an exemplary prior art circuit breaker 11. As is seen, when the prior art circuit breaker 11 is designed to be plugged in or removed, it will typically have a grip 1 to facilitate the user grabbing circuit breaker 11. The principles of circuit breaker operation are well known. Breaker contacts 8, 9 open in response to an over-current condition. The mechanism that opens breaker contacts 8, 9 is commonly known as an actuator.
An additional linkage mechanism (not shown in FIG. 1) couples the interior actuator mechanism (not shown in FIG. 1) to an actuator-handle 16. Actuator-handle 16 is also known in the prior art as a "handle" although sometimes the terms "actuator" or "actuator switch" are also used to describe actuator-handle 16. In the present application handle 16 is described as an "actuator-handle" to avoid potential confusion with the interior actuator mechanism and with grip 1.
The actuator-handle 16 provides several functions. First, the position of the actuator-handle 16 provides a visual indication of the operating state of the circuit breaker. Typically the actuator-handle 16 is mechanically coupled so that it rotates and/or translates relative to the surface of the circuit breaker to indicate the operating state of the circuit breaker. Additionally, the actuator-handle 16 is mechanically coupled to the actuator so that the user is able to manually set/reset the circuit breaker to an on-state or an off-state depending on the position of the actuator-handle. The actuator-handle 16 is useful, for example, to reset a circuit breaker after it has been tripped by an over-current condition. Additionally, the actuator-handle 16 is often used to intentionally cause the circuit breaker to be non-conducting, e.g., when maintenance or repair of the electronic system is planned. The actuator-handle 16 of a circuit breaker is commonly configured so that a slight pressure applied to the actuator-handle in its on-position results in the circuit breaker actuator-handle moving to a position where the current breaker is non-conducting.
A problem with the actuator-handle 16 of a conventional circuit breaker 11 is that its position may be inadvertently changed, resulting in the circuit breaker, and thus the electronic systems to which the circuit breaker is attached, being turned on or off at an inappropriate time. This is highly undesirable since it may result in damage to the electronic systems or may cause injury to users. Consequently, it is desirable in many applications to use a safety mechanism to prevent the inadvertent displacement of the handle.
FIG. 2A is an exploded perspective view of a prior art circuit breaker 11 with an actuator-handle 16 disposed in a slot 32 with two slot ends 32A, 32B corresponding to on/off states of the circuit breaker. A handle-guard 31, in the shape of a C-shaped spring clip 33 having S-shaped ends 34, 35 is designed to fit in slot 32. When the handle-guard 31 is in place, it protects actuator-handle 16 from being inadvertently displaced while still providing sufficient clearance for actuator-handle 16 to translate from its on-position to its off-position when an over-current condition is detected. Handle-guard 31 may be removed from slot 32 to enable the actuator-handle 16 to be manually repositioned.
FIG. 2B shows a partial side view of circuit breaker 11 with handle-guard 33 in place. The motion of the actuator-handle 16 to a tripped state is indicated in phantom. As can be seen in FIG. 2B, there is sufficient clearance that actuator-handle 16 is free to move underneath the bottom surface 31A of handle-guard 31. End surfaces 34, 35 of handle-guard 31 fit into end regions of slot 32, but are not rigidly connected to slot 32.
While the prior art handle-guard of FIG. 2A provides a safety benefit, it has several drawbacks. One drawback is that handle-guard 31 substantially blocks access to actuator-handle 16. Consequently, the user needs to remove handle-guard 31 every time they want to change the position of actuator-handle 16. Another drawback is that handle-guard 31 blocks a front (head-on) view of the position of actuator-handle 16. This may make it hard to determine the position of actuator-handle 16 where there is poor background lighting or in electronic systems where circuit breaker 11 is located close to a wall or other obstacle so that the user cannot obtain a side view of actuator-handle 16.
Conventional handle-guards 31 protect the actuator-handle 16 but do not provide a grip or grip surface. Commonly, a separate grip 1 is provided if the user is intended to grasp circuit breaker 11, e.g., when the circuit breaker is being installed in a breaker panel. Another problem with prior art circuit breakers is that there is no mechanism for ensuring that the circuit breaker is in a non-conducting state when the circuit breaker is installed or removed. It is comparatively easy for users to mistakenly install or remove a circuit breaker with the actuator-handle 16 in an on-position. This is a problem for all types of circuit breakers. However, it is likely to be a more severe problem for circuit breakers that are designed to be rapidly installed/removed, such as plug-in circuit breakers. Compact plug-in circuit breakers typically have male plug connections that are inserted or removed from female sockets in a base connector. This has the advantage that old circuit breakers may be quickly removed and new circuit breakers quickly installed. However, if the circuit breaker is removed/installed with the actuator-handle in an on-position, unwanted and undesirable electrical conduction may occur. For example, with the actuator-handle inadvertently positioned in an on-position, sparking may occur between the male plugs and female sockets when the male plugs are disposed a short distance from the female sockets during insertion or removal. Additionally, undesirable currents may flow if the circuit breaker is installed/removed with the actuator-handle inadvertently left in the on-position. For example, inserting a plug-in circuit breaker into its base may result in the premature flow of current in an electrical system if the actuator-handle is accidently positioned in the on-position. This may result in a current that causes damage to the electrical system and/or causes an electrical shock to the user.
Mechanical interlock means are one solution to the problem of inserting/removing plug-in circuit breakers. FIG. 3 shows a side view of a prior art circuit breaker with a mechanical apparatus to automatically turn-off (i.e., open the electrical contacts) of a circuit breaker whenever it is installed or removed. Plug-in circuit breaker 200 may have grips to facilitate a user grabbing circuit breaker 200. As shown in FIG. 3, a plug-in circuit breaker 200 has plugs 210 dimensioned to fit into sockets 220 of a base connector 280. A plunger 230 coupled by a spring 240 is dimensioned to fit into a plunger socket 225 which adjusts the position of a linkage mechanism 250, 260 so that actuator-handle 270 automatically is switched into an off-position whenever circuit breaker 200 is removed from base connector 280. The mechanical plunger apparatus shown in FIG. 3 provides an important safety benefit. However, it requires a comparatively complicated linkage mechanism. This increases the cost, complexity, and size of circuit breaker 200 compared to conventional plug-in circuit breakers lacking the desired safety interlock feature. Moreover, plunger 230 must be designed to have a long operating lifetime, i.e., not deteriorate during normal use. However, a spring plunger mechanism can degrade over time due to a variety of physical mechanisms, such as a change in spring characteristics of the spring, corrosion of moving parts, and dust/debris entering sockets and/or moving parts.
The previously described drawbacks of conventional handle-guards and mechanical interlocks are of particularly concern in the context of miniature plug-in circuit breakers used in distribution modules, such as those used in telecommunications applications. A conventional handle-guard, such as that shown in FIG. 2A may make it awkward to visually determine the state of the circuit breaker, particularly during removal/installation. A conventional safety plunger mechanism, such as that shown in FIG. 3, substantially increases the cost and complexity of a miniature plug-in circuit breaker. Moreover, combining the handle-guard of FIG. 2A with the safety plunger of FIG. 3 results in a circuit breaker that had the drawbacks of both safety devices.
What is desired is an improved safety device for plug-in circuit breakers that provides the benefits of protecting the actuator-handle from being inadvertently displaced during normal use while also ensuring that the actuator-handle is automatically switched to an off-state during insertion/removal of the circuit breaker.